Skin and core body temperatures

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facts and myths on radiant barrier

"As evidence of the importance of radiant heat exchange to the body’s thermal equilibrium, physiologists have discovered that living human skin has extraordinarily high absorptivity and emissivity (0.97), greater than almost any other known substance, matte-black metals included. Consequently, we are highly responsive to changes in mean radiant temperature."
Dr. A. Marsh


We have roughly 166,000 thermal receptors in our skin with most of them sensitive to heat loss.


Suggested reading:

Bacterial Diversity on Human Skin
Cortical, thalamic, and hypothalamic responses to cooling and warming the skin in awake humans
Sweat glands
Weschler on human skin interactions with indoor air
Skin Hydration: Ensuring Barrier Protection for the Healthcare Professional
Mean radiant temperature (MRT)
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Radiant based HVAC
IEQ Research using thermal manikins
Introduction: Fundamentals of Indoor Environmental Quality
Skin science for the kids
Thermal Manikins
Health and HVAC systems
Health Effects and IEQ

Floor Temperatures
Radiant asymmetry
Humidity
Thermal Comfort Tool


We don't inhale comfort, we feel it through our skin. Inhalation is part of the respiratory process and relates to indoor air quality not thermal comfort.

Forced air system excel at condition the air, that is they are very good at:

decontamination,
deodorization and
de(humidification),

but only radiant based HVAC systems are effective at conditioning the skin for thermal comfort.



Illustration showing the influence of building enclosure performance on thermal comfort and specifically the mean radiant temperature.



Illustration showing an operative temperature using various combinations of dry-bulb temperature and mean radiant temperature.


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Facts About Your Skin - Temperatures in and on the human body
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We don't feel the heat loss from the building, but the heat loss from our skin ergo we don't condition the building, we condition the body. Learn more about human anatomy, physiology and thermal comfort.

Vasodilatation & Sweating


Animation1 of vasodilatation (increase in blood flow) and sweating (skin wettedness).
Credit/Copyright : This image is made available through permission granted by Arizona State University
 

Goosebumps

goose bumps are response to indoor environmental quality
Credit/Copyright : Martin Dohrn / Science Photo Library
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Sweat pores

sweating  - physical responses to indoor environmental quality which can be controlled with radiant based HVAC systems.
Credit/Copyright : Eye of Science / Science Photo Library
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Skin temperatures


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The Skin
Credit/Copyright : Surface Area of Human Skin The Physics Factbook™

The human body's largest organ is the skin. Skin protects body tissues against injuries and helps regulate body temperature by making the pores larger or smaller. The nerves in skin receive the stimuli that are then interpreted by the brain as touch, heat, and cold. Skin is composed of three layers: epidermis, dermis, and subcutaneous fatty tissue.

The interface between the epidermis and dermis is extremely irregular and consists of a succession of papillae, or fingerlike projections, which are smallest where the skin is thin and longest in the skin of the palms and soles. The papillae of the palms and soles are associated with elevations of the epidermis, which produce ridges that are the basis for fingerprint identification.

Subcutaneous fatty tissue is the deepest layer of the skin. It is composed of connective tissue, blood vessels, and fat cells. This layer binds the skin to underlying structures, insulates the body from cold, and stores energy in the form of fat.

The skin forms a protective barrier against the action of physical, chemical, and bacterial agents on the deeper tissues and contains the special end organs for the various sensations commonly grouped as the sense of touch. Through the activity of its sweat glands and blood vessels, it is important in maintaining body temperature. One square inch (6.5 square centimeters) of skin contains up to 4.5 m of blood vessels, which have as one of their functions the regulation of body temperature. The skin varies in thickness from 0.5 mm on the eyelids to 4 mm or more on the palms and soles.

More about your skin:

The typical body has between 20 ft2 to 22 ft2 of surface area which serves as a radiator for releasing heat via radiation to lower the body temperature or as an absorber to take in radiant energy to raise the body temperature. The skins emissivity is around 0.97 which makes it almost perfect as a radiator and absorber.

Quotes

"There is no normal temperature but a range over which temperature fluctuates and changes."
Dr. Tim Lowenstein

"...your skin temperature varies parabolically from 83 deg F. (28.2 C) at an ambient temperature of 49 deg F. (9.5 C) to 98 deg F. (37.2 C) at an ambient temperature of 95 deg F (35 C)." Dr. K.R. Koehler College Physics for Students of Biology and Chemistry, University of Cincinnati

More about core body temperatures:

"When summarizing studies with strong or fairly strong evidence the range for oral temperature was 33.2–38.2C, rectal: 34.4–37.8C, tympanic: 35.4– 37.8C and axillary: 35.5–37.0C. The range in oral temperature for men and women, respectively, was 35.7–37.7C and 33.2–38.1C, in rectal 36.7–37.5C and 36.8–37.1C, and in tympanic 35.5–37.5C and 35.7–37.5C." Sund-Levander, Mrtha; Christina Forsberg and Lis Karin Wahren. Normal oral, rectal, tympanic and axillary body temperature in adult men and women: a systematic literature review. Scandinavian Journal of Caring Sciences. Vol. 16 No. 2 (June 2002): 122.

"Skin is the principal organ for dissipating heat: the human body dissipates
approximately 85% of its heat loss through the skin under normal environmental
conditions (Zhang 2003)."
Holopainen, R., A human thermal model for improved thermal comfort, Doctor of Science in Technology Thesis, Aalto University, VTT, December 2012

Bibliography/endnotes

1. Copyright (c) 2005, Arizona State University, All Rights Reserved, Republished by www.healthyheating.com with restricted permission from ASU.



Related reading:

Thermal Comfort: A Condition of Mind
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